Combine first 5 ingredients in a 13- x 9- x 2-inch baking dish. Place fillets in dish, turning to coat well. Cover and let stand, skin side up, at least 30 minutes at room temperature.
Turn fish, skin side down, in baking dish. Sprinkle with nutmeg and pepper. Bake, uncovered, at 400° for 25 minutes or until fish flakes easily when tested with a fork, basting occasionally with pan juices.
Transfer fillets to a serving platter. Garnish with orange slices and mint leaves. Serve immediately.